The overriding purpose of the proposed randomized trial is to examine the effectiveness of a promising and efficient outpatient treatment of adolescent substance abuse delivered in a community-based treatment setting. Although several evidence-based treatments of adolescent substance abuse are emerging (see e.g., Waldron & Turner, 2008), none have experienced widespread adoption in community settings. Thus, as noted by the Institute of Medicine (1998) more than a decade ago and reiterated more recently (e.g., McCarty et al., 2007), a considerable science-service gap exists in regards to treatment of substance abuse in adolescents and adults. For the proposed study, 204 adolescents meeting diagnostic criteria for substance abuse or dependence will be randomized to either the Contingency Management-Family Engagement (CM-FAM; Henggeler et al., 2012) or Treatment as Usual (TAU) conditions. A multimethod, multirespondent approach will be used to track clinical outcomes at 3, 6, 9, 12, and 18 months post recruitment. Clinical level outcomes pertain to youth substance use, criminal behavior, mental health functioning, and key mediators of serious antisocial behavior in adolescents (e.g., self-control, parental supervision, associatio with deviant peers). In addition, the incremental cost of CM-FAM will be determined for use in cost effectiveness analyses. Aim 1: Over an 18-month post-recruitment follow-up, determine the relative effectiveness of CM-FAM vs. TAU in reducing adolescent participants' substance use, criminal activity (including incarceration), and mental health symptoms; and evaluate the cost effectiveness of CM-FAM in achieving these outcomes. Aim 2: Examine possible moderators and mediators of intervention effectiveness. Moderator variables will include youth demographic and clinical (e.g., co-occurring disorders) characteristics. Mediator variables will include measures of self-control, parenting, and association with deviant peers - constructs targeted by CM- FAM.